A new version of Apple's iOS for its tablets and phones was rushed
out the door Friday to patch the vulnerability, wherein its mobile,
tablet and desktop software is not doing SSL/TLS hostname checking —
communications meant to be encrypted, are not.

The patch has only been issued for the more recent iPhones (4 and later), iPod touch (5th generation) and iPad (2nd generation).

Security researchers across several communities believe that Mac
computers are even more exposed, as they are currently left hanging
without a patch.

(Quoted from Apple's published source code.)
Note the two goto fail lines in a row. The first one is
correctly bound to the if statement but the second, despite the
indentation, isn't conditional at all. The code will always jump to the
end from that second goto, err will contain a successful value
because the SHA1 update operation was successful and so the signature
verification will never fail.

If you're worried your system may be affected, follow the link above to Imperial Violent, who has created a tool to do a quick check.